A cannula is commonly used to introduce a catheter into a body cavity, such as a blood vessel. After the catheter has been inserted into the body cavity, the cannula, if left in place, may interfere with a surgical field. Removal of the cannula, therefore, is often desired. However, it is sometimes difficult to remove the cannula due to frequently enlarged proximal end of the catheter. This problem has been alleviated by splitable cannulas, which can be removed from a patient's blood vessel by separating into two parts, as described in U.S. Pat. Nos. 4,865,593, 5,104,388, and 5,318,542, all of which are incorporated herein by reference. Although the disclosed splitable cannulas are easy to remove, they all require an access mechanism to incise the blood vessel for insertion. Moreover, a distal end of a catheter, housed within the splitable cannula, often protrudes from the distal end of the cannula, and thus can be damaged by sometime calcific plaque of the blood vessel walls.
A need, therefore, exists for a cannula system which provides easy access, protection, and insertion of a medical device into a body tissue, and is removable by sliding.